Advances in wireless access schemes and wireless networks for cellular mobile communication (hereinafter designated “Long Term Evolution (LTE)” or “Evolved Universal Terrestrial Radio Access (EUTRA)”) are being investigated in the 3rd Generation Partnership Project (3GPP). With LTE, an orthogonal frequency-division multiplexing (OFDM) scheme is used as the communication scheme for the downlink from a base station device to a mobile station device. Also, a single-carrier frequency-division multiple access (SC-FDMA) scheme is used as the communication scheme for the uplink from a mobile station device to a base station device. Herein, in LTE, a base station device is also designated Evolved Node B (eNodeB), and a mobile station device is also designated User Equipment (UE). LTE is a cellular communication system that plurally arranges areas covered by base station devices into cells.
In LTE, a base station device uses 72 subcarriers in the center of a cell to transmit a synchronization signal (SS) and a physical broadcast channel (PBCH). In LTE, a mobile station device conducts a cell search using a synchronization signal, and acquires time timings, frequency timings, and a physical layer cell identity (PCI). In LTE, after a cell search, the mobile station device uses the physical broadcast channel to acquire a master information block. The master information block is system information. In addition, the master information block includes information indicating the downlink bandwidth of the cell as well as information indicating a system frame number (SFN), and the like. A system frame is also designated a radio frame.
In LTE, after receiving the PBCH, a mobile station device uses a physical downlink shared channel (PDSCH) to acquire multiple system information blocks. The system information blocks are system information. In addition, the system information blocks include radio resource configuration information that is common for multiple mobile station devices. A base station device transmits a single system information block using a single PDCCH.
In LTE, a base station device assigns a portion of the downlink band of a cell to the PDSCH. Also, in LTE, a base station device transmits downlink control information (DCI) used to schedule a single PDSCH using a single physical downlink control channel (PDCCH). Also, in LTE, a base station device transmits downlink control information used to schedule a PDSCH that transmits a system information block with a PDCCH in a common search space. The common search space is used for PDCCH transmission which common for all mobile station devices. In LTE, all mobile station devices monitor the common search space for a PDCCH.
In LTE, a mobile station device configures a physical random access channel (PRACH) on the basis of radio resource configuration information included in system information blocks. In LTE, after configuring the PRACH, a mobile station device starts a random access procedure, and adjusts the uplink transmission timings. In LTE, after adjusting the uplink transmission timings, a mobile station device transmits a connection request message to a base station device, and starts an initial connection establishment.
In LTE, a technology is used in which a mobile station device and a base station device communicate by using multiple cells (component carriers) with the same channel structure (cell aggregation, also designated carrier aggregation). For example, with communication using cell aggregation, a mobile station device and a base station device are able to use multiple cells to transmit and receive on multiple physical channels at the same time. For example, after a mobile station device and a base station device conduct initial connection establishment in one cell, the base station device is able to add cells to be used for communication with that mobile station device.
In 3GPP, in order to improve spectral efficiency, the introduction of non-backward compatible component carriers is being investigated. On a non-backward compatible component carrier, at least one of the synchronization signal, PBCH, PDCCH, and system information block is not transmitted (NPL 1). Consequently, a mobile station device and a base station device are required to conduct initial connection establishment on one backward compatible component carrier, and afterwards add a non-backward compatible component carrier to be used for communication between the base station device and the mobile station device. In other words, a non-backward compatible component carrier is required to be part of a component carrier set that includes at least one backward compatible component carrier. Backward compatible component carriers are the component carriers that have been used in LTE heretofore.
In addition, in 3GPP, the use of an enhanced physical downlink control channel (E-PDCCH) to transmit downlink control information is being investigated in order to increase the number of terminals that a single base station is able to serve. The E-PDCCH is mapped to the PDSCH space. Additionally, in 3GPP, the introduction of technologies such as beamforming and spatial multiplexing with respect to the E-PDCCH are being investigated.